diff --git a/src/IFoxCAD.Cad/ExtensionMethod/Curve3dEx.cs b/src/IFoxCAD.Cad/ExtensionMethod/Curve3dEx.cs
index 226e5de516e299e8315e9e1efa3c7e188ab02400..870fdbda7869c4be5630c7471d5c7c40a0176595 100644
--- a/src/IFoxCAD.Cad/ExtensionMethod/Curve3dEx.cs
+++ b/src/IFoxCAD.Cad/ExtensionMethod/Curve3dEx.cs
@@ -1,4 +1,4 @@
-namespace IFoxCAD.Cad;
+namespace IFoxCAD.Cad;
 
 /// <summary>
 /// 三维解析类曲线转换为三维实体曲线扩展类
@@ -16,7 +16,46 @@ public static bool IsEqualPoint(this Tolerance tol, double d1, double d2)
     {
         return Math.Abs(d1 - d2) < tol.EqualPoint;
     }
-
+        /// <summary>
+        /// 判断点与另外两点的位置关系
+        /// </summary>
+        /// <param name="pt0"></param>
+        /// <param name="pt1"></param>
+        /// <param name="pt2"></param>
+        /// <param name="dTol"></param>
+        /// <returns></returns>
+        /// 
+        public static PtOnlineType IsOnLine(this Point3d pt0, Point3d pt1, Point3d pt2, double dTol)
+        {
+            var value = PtOnlineType.OutLineP12;
+            double d12 = Math.Abs(pt1.DistanceTo(pt2));
+            double d01 = Math.Abs(pt0.DistanceTo(pt1));
+            double d02 = Math.Abs(pt0.DistanceTo(pt2));
+            if (d12 == d01+d02) value = 0;
+            if (d02 == d01+d12)
+            {
+                if (d01 <= dTol)
+                {
+                    value = PtOnlineType.OnLineP1N;
+                }
+                else
+                {
+                    value = PtOnlineType.OnLineP1W;
+                }
+            }
+            if (d01 == d02+d12)
+            {
+                if (d02 <= dTol)
+                {
+                    value = PtOnlineType.OnLineP2N;
+                }
+                else
+                {
+                    value = PtOnlineType.OnLineP2W;
+                }
+            }
+            return value;
+        }
     #region Curve3d
 
     /// <summary>